Flotation apparatus



Dec. 12, 1961 H. u. ZIEMER 3,012,672

FLOTATION APPARATUS Filed Aug. 31, 1959 6 Sheets-Sheet 1 I fans a Zz'erzzer Dec 12, 1961 H. u. ZIEMER 3,0

FLOTATION APPARATUS Filed Aug. 31, 1959 6 Sheets-Sheet 2 Dec. 12, 1961 H. u. ZIEMER 3,012,672

FLOTATION APPARATUS Filed Aug. 31, 1959 6 Sheets-Sheet 4 FIEA:

firzfeizzors 190/75 a 213227237" Dec. 12, 1961 H. u. ZIEMER FLOTATION APPARATUS 6 Sheets-Sheet 5 Filed Aug. 31. 1959 mam Dec. 12, 1961 H. u. ZIEMER 3,

FLOTATION APPARATUS Filed Aug. 31. 1959 6 Sheets-Sheet 6 Unite The present invention generally relates to the art of beneficiating materials by flotation techniques. More particularly, it relates to a novel apparatus for beneflciating ores and other substances by flotation.

The beneficiation of ores by froth flotation techniques is of great importance to the ore beneficiation art. The flotation process is widely used for treating metallic and non-metallic ores and, in addition, is receiving an ever widening application in other industries.

In many of the prior art flotation machines, the mineral feed, which is usually in the form of an aqueous pulp, is introduced horizontally into a flotation cell which is usually constructed substantially in the form of a cylinder or prism. The pulp is agitated and aerated in the flotation cell by a rapidly rotating impeller which rotates on a substantially vertical axis. The mineral-laden air bubbles separate from the other material and pass upwardly to the pulp level of the flotation cell to form a froth which is floated olfof the top of the cell.

Since the pulp is introduced laterally into such a flotation cell, in which the air bubbles are passing chiefly in an upward direction, it has been diflicult because of this difference in the directions of flow to obtain a uniform distribution of air bubbles throughout the cross-section of the cell. It has also been diflicult to float mineral particles of relatively large mass in such a flotation cell.

A different type of flotation cell has recently been developed which remedies some of the shortcomings of many of the prior art flotation machines. This new flotation cell is described in detail in copending US. patent application Serial No. 754,765, filed August 13, 1958, now US. Patent No. 2,922,521, issued January 26, 1960. The apparatus described in the copending patent application includes an inlet conduit for containing a flowing stream of fluid, and a laterally diverging vertical conduit connected to the inflow conduit adjacent the outflow end thereof for receiving the flowing stream of fluid from the inflow conduit. The laterally diverging conduit cornprises a part of the flotation cell. A pump is connected in the inflow conduit line for pumping the flotation cell feed through the inflow conduit into the laterally diverging conduit. An overflow is provided adjacent to the upper end of the flotation cell. The present invention is directed to improvements in such flotation apparatus.

When using such apparatus, it has been possible, becauseof air and pump thrust upwardly into the diverging conduit, to effect a higher weight recovery of materials than can be obtained in more conventional flotation cells; for example, such cells as are used in Fagergren and Denver flotation machines.

In the flotation apparatus described in application Serial No. 754,765, a single overflow is provided along one wall of the flotation cell. Particles in the froth opposite to this one wall, therefore, must travel across the entire upper surface of the liquid in the flotation cell before reaching the overflow and discharging from the flotation cell. Some of the particles, particularly the larger size particles, tend to drop out of the froth while traveling this distance, thereby reducing the recovery from the flotation cell. The present invention provides an apparatus in which the froth is more readily removed and in which the particles in the froth only need travel a relatively shorter distance than in the previous apparatus described in the copending application.

States Patent Patented Dec. 12, 1961 It is, accordingly, an object of the present invention to provide a novel apparatus for beneficiating ores.

It is a further object of the invention to provide a new flotation apparatus which achieves efficient removal of the froth from the flotation cell.

It is another object of the invention to provide a new flotation machine having a diverging conduit flotation cell with a plurality of froth removal means provided adjacent the upper end of the flotation cell.

These and further objects and advantages of the present invention will be apparent from the following description and accompanying drawings which illustrate embodiments of the invention.

In the drawings:

FIGURE 1 is a plan view of one form of flotation apparatus embodying certain of the features of the invention;

FIGURE 2 is a sectional view taken substantially along line 2-2 of FIGURE 1;

FIGURE 3 is a side elevational view, partially broken, of the flotation apparatus shown in FIGURES 1 and 2;

FIGURE 4 is a plan view of a flotation cell, generally similar to that illustrated in FIGURES l to 3, embodying another form of froth removal means, in accordance with this invention;

FIGURE 5 is a partial front elevational view of the apparatus illustrated in FIGURE 4;

FIGURE 6 is a partial side elevational view of the apparatus illustrated in FIGURE 4;

FIGURE 7 is a partial sectional view taken substantially along line 77 of FIGURE 4;

FIGUURE 8 is a partial sectional view taken substantially along line 88 of FIGURE 4; and

FIGURE 9 is a partial sectional view taken substantially along line 99 of FIGURE 4.

As will hereinafter appear, the above-stated objects of the invention are accomplished by the provision of a plurality of froth removal means adjacent the upper end of a vertical rigid-walled laterally diverging conduit flota-' tion cell. The invention makes possible more effective removal of the froth from diverging conduit flotation cells, than has heretofore been attained.

The apparatus of the present invention is eminently useful for the flotation beneficiation of potash ores such as sylvite, sylvinite, langbeinite, mixed potash ores, etc., phosphate ores, and the like. The apparatus operates etflciently at high throughputs. The apparatus also makes possible the beneficiation of larger ore particles than are usually beneficiated in conventional flotation machines.

In general, the flotation apparatus of this invention comprises an inflow conduit for containing a flowing stream of fluid, a laterally diverging conduit connected to the outflow end thereof for receiving the stream of fluid from the inflow conduit, and a plurality of froth removal means adjacent the upper end of the laterally diverging conduit. By providing a plurality of froth removal means adjacent the upper end of the laterally diverging conduit, the floated particles are rapidly removed from the flotation cell and the recovery of the floated constituent is increased. structures illustrated in the drawings are merely illustrative embodiments of the general principles involved.

The apparatus provides a flotation cell having a bottom inlet and a plurality of overflows adjacent to the upper end of the flotation cell. Between the inlet and over flows, the flotation cell is defined by a rigid-walled laterally. diverging conduit section. The inflow conduit opens centrally or substantially centrally into the flotation cell from below and the pulp-air mixture emerges from the inlet conduit as a jet stream and rises in the flotation cell. The air-laden mineral particles continue to rise in the cell to the pulp level. I

It is to be understood that the particular Since the jet stream carries the solid entrained particles mainly vertically upwardly in the same direction that the air bubbles are rising, the adherence of the solid particles to the air bubbles is greatly facilitated and at the same time a shaking or shearing of the solid particles from the air bubbles is substantially reduced. For this reason, the apparatus enables a reliable flotation of even unusually large or so-called coarse particles with high efliciency. The coarser particles, however, tend to drop out of the froth and, in accordance with the present invention, means are provided adjacent the upper end of the flotation cell to remove the froth product more rapidly than in the flotation cell described in the copending application Serial No. 754,765. The flotation cell is also provided with an outflow conduit connected to a lower portion of the cell through which non-floated material may be withdrawn from the cell. A control valve is connected in the outflow conduit and the control valve is operatively connected to the fluid in the flotation cell.

A flotation apparatus embodying the principles of this invention is illustrated in FIGURES l, 2 and 3 of the drawings. Another embodiment is illustrated in FIG- URES 4, 5, 6, 7, 8 and 9 of the drawings. In both embodiments many of the items of apparatus are the same and corresponding numbers are used to designate these items. Referring to the drawings, the apparatus illustrated includes an inflow conduit 11 which is connected to the bottom of a rigid-walled, laterally diverginng conduit or flotation cell 13. The main flotation cell 13 is illustrated as an inverted pyramid having a rectangular cross section; however, the diverging conduit may take on other forms such as an inverted cone. The cell 13 has a substantially vertical axis and the walls thereof diverge laterally with increasing elevation. The point angle of the cell is preferably from about 20 to about 50. The cell also preferably has a height from about 1.5 to about 3.5 times the width of the cell. The inflow conduit 11 is also a discharge conduit of a pump 15. The inflow conduit 11 extends vertically upwardly and has an extension 17 (FIG. 2) into the flotation cell. In general, the length of the extension 17 into the flotation cell depends upon the feed rate and the ratio of floated material to non-floated material. For example, when beneficiating different materials at substantially the same inflow conditions, if the ratio changes from 1:2 to 1:4, the extension 17 is preferably of relatively longer length in the latter operation. The flotation cell 13 is provided with an inclined bottom 19 spaced below the outlet opening of the extension 17. The flotation cell 13 has connected adjacent its lowermost point an outflow conduit 21 through which non-floated material may be withdrawn from the flotation cell. In order to efficiently drain the flotation cell when the cell is not in operation, the lower part of the outflow conduit 21 is in substantial alignment with the inclined bottom 19 and is connected to the flotation cell 13 at the lowermost point of the inclined bottom.

The flotation cell 13 is provided at the top with vertical walls 23, 25, 27 and 2.9 which together form a froth box on the flotation cell. Oppositely positioned overflow or froth discharge means 31 and 33 are provided adjacent the top of the cell 13. Each of the overflow means, 31 and 33, illustrated, includes an overflow weir 41 and a cleaner chamber or funnel 35. Each funnel 35 has a chute 37 which directs the froth from the funnel to a discharge trough 39. The upper edge of the opposite walls 25 and 29 of the froth box on the flotation cell 13 are at a lower elevation than the upper edge of the other walls 23 and 27. An overflow weir 41, having a substantially horizontal overflow surface is suitably fixed in each of the lower walls 25 and 29, and extends above the upper edge of the wall. The weirs 41 are preferably adjustable in elevation or height by means not shown. When the cell is in operation, froth overflows these weirs 41. A curved guide plate 43 is connected to the top of each of the lower walls 25 and 29 and curves downwardly to the cleaner chamber or funnel 35. The funnels 35, illustrated, like the main cell 13, are of rectangular cross section and the upper edge of the inside vertical wall 45 of each funnel is connected to the adjacent guide plate 43. Each funnel has four vertical walls which form a froth box on the funnel. The inside Wall 45 and the outside wall 47 are parallel. The other two parallel walls are extensions of walls 23 and 27 of the flotation cell 13 and, therefore, the same numbers designate these walls. The four vertical walls together form a froth box on the funnel 35.

The outside wall 47 of each funnel is at a lower elevation than the walls 23 and 27 and is provided at its top edge with a discharge chute 37 which receives the discharge froth from the froth box of the funnel and delivers it to the discharge trough 39. The outside wall 47 is preferably provided on the outside with a weir 49 which is preferably vertically adjustable by means not illustrated. The top edge of the weir 49 is provided with a downwardly and inwardly inclined plate 51 over which a rotatable paddle wheel 53 is positioned. When in operation, the paddle wheels 53 rotate in the direction shown by the arrow A so as to aid in moving the froth into the trough 39. A recycle conduit 55 connects the bottom of each of the funnels 35 to a fresh feed inlet conduit 57 which is connected to the suction end of the pump 15. An air inlet conduit 59 is also connected into the fresh feed inlet conduit 57. This conduit 59 has a throttle flap 61 therein for regulating the flow within the conduit 59. Aerating air is introduced into the inlet conduit 57 via conduit 59 to aerate the aqueous pulp being drawn into the suction end of the pump 15.

A control valve 63 (FIG. 3) is positioned in the outflow conduit 21 through which non-floated material or tailings may be withdrawn from the flotation cell 13. It has been determined that the operation of the flotation cell may be efliciently controlled by controlling the rate of trailing withdrawal through the outflow conduit 21. The control valve 21 adjustably controls this rate of withdrawal. The control valve 63 is operatively connected to the fluid in the flotation cell 13. The operation of the flotation cell 13 is preferably controlled by adjusting the rate of tailing withdrawal so as to maintain a substantially constant predetermined pulp density in the flotation cell and preferably in the lower portion of the flotation cell when the cell is in operation. The control valve 63 is, therefore, preferably operatively connected to the lower interior of the cell, that is to the fluid in the lower portion of the flotation cell 13, in a manner to obtain a substantially constant predetermined pulp density in the lower portion of the cell 13. The control valve is preferably rubber lined so as to reduce corrosion of the valve. In the illustrated embodiment, the opening or closing of the control valve 63 is controlled by an automatic control device 65 which is diagrammatically illustrated in the drawing since such devices are well known and the specific construction of the device 65 forms no part of the invention. The control device 65 is operatively connected to the valve 63 by line 67. The control device 55 is also operatively connected to the material in the lower portion of the flotation cell 13 by line 69. When the flotation apparatus is in operation, the device 65 receives a signal through line 69 which is proportional to the pulp density in the lower portion of the flotation cell and the control device 65 converts the signal into a form which adjusts the amount of opening of the control valve 63 thereby adjusting the rate of withdrawal of tailing through the outflow conduit 21. The control valve 63 is controlled by the control device 65 in a manner such that when the pulp density in the lower portion of the flotation cell is above the predetermined pulp density which it is desired to maintain, the valve is in a relatively more open position and the rate of withdrawal of pulp through line 21 is greater than when the pulp density is at the predetermined density. Similarly, the control valve 63 is controlled by the control device 65 in a manner such that when the pulp density in the lower portion. of the flotation cell is below the predetermineddensity which it is desired to maintain, the valve 63 is in a more relatively closed position and the rate of. withdrawal of pulp through conduit 21 is less than when the pulp density is at the predetermined point.

When the apparatus is in use in a froth flotation operation, the mineral-laden air bubbles in the flotation cell 13 rise to the pulp level in the flotation cell, that is, the air bubbles move chiefly in a vertical direction. However, since the walls of the cell 13 diverge, the mineralladen air bubbles also have a lateral motion, that is, the air bubbles also tend to move outwardly from the center line of the cell toward the side walls. By providing a plurality of froth overflow means, this lateral motion of. the mineral-laden air bubbles is taken advantage of since the bubbles may continue their lateral motion to the overflow from the cell. In the apparatus described in the application Serial No. 754,765, the air bubbles having a lateral velocity component toward the wall opposite the overflow were required to change their direction upon reaching the pulp level in order to reach the overflow from the cell. The air bubbles, therefore, not only had to travel a greater distance to the overflow, but also had to change their direction of motion, as compared to the motion of the mineral-laden air bubbles when using the present apparatus in a froth flotation operation.

As hereinbefore set forth, the larger or coarser floated particles tend to drop out of the froth and unless the froth is rapidly removed, the yield of coarse particles will be reduced. The particles that drop out of the froth into the main flotation cell may not be subsequently refloated and may, therefore, be withdrawn through the outflow conduit connected to the lower part of the cell. The particles that drop out of the froth into the funnel of the cleaner chamber will be recirculated through the pump and back into the main flotation cell. Such recirculation is, however, generally undesirable since it increases the recycle load. Further, when it is desirable to recover large granules of a fragile material, such as sylvite or langbeinite, the pump action tends to reduce the particle size thereby reducing the ultimate recovery of coarser particles. The apparatus of the present invention rapidly removes the froth and, therefore, the extent of these undesirable effects is reduced.

In the apparatus illustrated in FIGURES 4 through 9 of the drawings, the lateral velocity of the air bubbles is taken advantage of even more completely since in the apparatus illustrated in FIGURES 4 through 9, an annular overflow means 71 is provided adjacent the upper end of the flotation cell 13 to receive the froth overflow from the main flotation cell 13. Referring more particularly to FIGURES 4 to 9 of the drawings, the illustrated apparatus embodies many of the same features of apparatus decribed in connection with the embodiment illustrated in FIGURES 1 to 3, and, as hereinbefore set forth, the same numerals are used to designate similar pieces of apparatus. The flotation cell 13, illustrated in FIGURES 4 to 9, is provided at the top with vertical walls 73, 75, 77, and 79, which together form a square froth box on the flotation cell. The upper edge of each of these walls is at substantially the same elevation. An overflow weir 81 is suitably fixed in each of the walls 73, 75, 77, and 79, and each weir extends above the upper edge of the wall in which it is secured. These weirs, as the weirs 41, are preferably adjustable in height by means not shown. When the cell is in operation, froth overflows these weirs 81. It is preferable that each weir touches the adjacent perpendicular weir thereby providing in effect an annular weir surrounding the upper end of the flotation cell 13. The overflow weirs have a substantially horizontal overflow surface which enables the material overflowingthe cell, to overflow in directions.

As. shown in FIGURE 4 by the, arrows, when the cell is in operation, the frothoverflowing the weirs. 81 is split with substantially half of the froth passing to the left (FIG. 4) toward the funnel 35, illustrated in the left half of the drawing, While the other half flows to theright toward the funnel 35 illustrated in the right half of the drawing. A curved guide plate 83, 85, 87, and -89 is connected to the top of each of the walls 73, 75, 77, and 79, respectively, and curves downwardly and outwardlyfrom the flotation cell 13. The material passing over the lower guide plate 83 (FIG. 4) is split by a vertical divider wall 91 and the material passing to the left of the wall 91 is directed into a trough 93 which is connected to the funnel 35 illustrated in the left half of FIGURE 4. Likewise, the material passing to the right of the vertical divider wall 91 drops into a trough 95' which ultimately carries the material into the funnel 35 illustrated in the right half of FIGURE 4. Similarly, the material overflowing the weir 81 positioned in the wall 77 and passing down the curved guide plate 87 is split by a vertical divider wall 97 with the material passing to the left of the wall 97 being directed into a trough 99 which ultimately carries the material into the funnel 35, illustrated in the left half of FIGURE 4. The material passing to the right of wall 97 is directed into a trough 101 which carries the material into the funnel 35 illustrated in the right half of FIGURE 4.

Each of the troughs 93, 95, 99, and 101 has an inclined bottom which is inclined away from respective dividing wall 91 or 97. This is clearly illustrated in FIG- URES 5, 7, and 9. Referring to FIGURE 9, it may be seen that the trough 99 has an inclined bottom 193 which is inclined downwardly from the partition wall 97 to the adjacent connecting funnel 35. In a similar manner, the trough 101 has an inclined bottom 105 which is inclined downwardly away from the dividing Wall 97 toward the adjacent funnel 35. The funnels 99 and 191 have a common outside vertical wall 107 and similarly the troughs 93 and 95 have a common outside vertical wall 109. These vertical walls It)? and 109' in part provide a froth box which receives the froth overflowing from flotation cell 13. The construction of the funnels 35, overflow chutes 37, troughs 39, and other features of apparatus of the embodiment illustrated in FIGURES 4 to 9, are generally similar to those described in the embodiment illustrated in FIGURES 1 to 3.

The apparatus of this invention achieves an efiicient removal of the froth from the main flotation cell 13. The use of the apparatus in a flotation operation enables a high recovery of unusually coarse particles to be achieved. The plurality of overflow means efliciently utilizes the lateral velocity of the air bubbles.

The description of the invention utilized specific reference to certain construction details; however, it is to be understood that such details are illustrative only and not by way of limitation. Other modifications and equivalents of the invention will be apparent to those skilled in the art from the foregoing description.

Having now fully described and illustrated the invention, what is desired to be secured and claimed by Letters Patent is set forth in the appended claims.

1. Flotation apparatus comprising a vertical rigidwalled laterally diverging conduit flotation cell having a substantially centrally positioned bottom inlet, said diverging conduit diverging with increasing elevation, a substantially vertical inflow conduit connected to the bottom inlet of said flotation cell to introduce a vertically upwardly directed stream of fluid into the cell, an outflow conduit connected to a lower portion of said flotation cell for Withdrawing all non-froth material from said cell, and two overflow means at substantially the same elevation adjacent the upper end of said flotation cell, said two overflow means being positioned substantially opposite to each other, each of said overflow means including a weir having a substantially horizontal overflow surface and a funnel adjacent to each weir to receive material overflowing the weir, each funnel being connected to return all non-froth material to said inflow conduit, and a froth receiving trough on the side of each funnel opposite its associated Weir with a froth weir between said froth trough and funnel.

2. Flotation apparatus comprising a vertical rigidwalled laterally diverging conduit flotation cell having a substantially centrally positioned bottom inlet, said diverging conduit diverging with increasing elevation, a substantially vertical inflow conduit connected to the bottom inlet of said flotation cell, an outflow conduit connected to a lower portion of said flotation cell, for withdrawing all non-froth material from said cell, a control valve in said outflow conduit operatively connected to the fluid in the flotation cell to regulate withdrawal of material to maintain a substantially constant density of the material in the lower portion of the cell, two separated over- 20 flow means adjacent the upper end of said flotation cell,

said overflow means being positioned substantially oppo-' site to each other, each of said overflow means including a weir having a substantially horizontal overflow surface and a funnel adjacent to each weir to receive material overflowing the weir, each funnel being connected to return all non-froth material to said inflow conduit, and a froth receiving trough on the side of each funnel opposite its associated weir with a froth weir betwecn 'saidfroth trough and funnel.

References Cited in the file of this patent UNITED STATES PATENTS 1,732,893 Hunt Oct. 22, 1929 2,142,207 Price Jan. 3, 1939 2,324,018 Peterson Feb. 5, 1941 2,733,809 Werge et al. Feb. 7, 1956 2,922,521 Schranz Jan. 26, 1960 2,931,502 Schoeld et al Apr. 5, 1960 FOREIGN PATENTS 602,202 France Mar. 15, 1926 

1. FLOTATION APPARATUS COMPRISING A VERTICAL RIGIDWALLED LATERALLY DIVERGING CONDUIT FLOTATION CELL HAVING A SUBSTANTIALLY CENTRALLY POSITIONED BOTTOM INLET, SAID DIVERGING CONDUIT DIVERGING WITH INCREASING ELEVATION, A SUBSTANTIALLY VERTICAL INFLOW CONDUIT CONNECTED TO THE BOTTOM INLET OF SAID FLOTATION CELL TO INTRODUCE A VERTICALLY UPWARDLY DIRECTED STREAM OF FLUID INTO THE CELL, AN OUTFLOW CONDUIT CONNECTED TO A LOWER PORTION OF SAID FLOTATION CELL FOR WITHDRAWING ALL NON-FROTH MATERIAL FROM SAID CELL, AND TWO OVERFLOW MEANS AT SUBSTANTIALLY THE SAME ELEVATION ADJACENT THE UPPER END OF SAID FLOTATION CELL, SAID TWO OVERFLOW MEANS BEING POSITIONED SUBSTANTIALLY OPPOSITE TO EACH OTHER, EACH OF SAID OVERFLOW MEANS INCLUDING A WEIR HAVING A SUBSTANTIALLY HORIZONTAL OVER- 